Effects of Charge Sequence Pattern and Lysine-to-Arginine Substitution on the Structural Stability of Bioinspired Polyampholytes

A comprehensive study focusing on the combined influence of the charge sequence pattern and the type of positively charged amino acids on the formation of secondary structures in sequence-specific polyampholytes is presented. The sequences of interest consisting exclusively of ionizable amino acids (lysine, K; arginine, R; and glutamic acid, E) are (EKEK)₅, (EKKE)₅, (ERER)₅, (ERRE)₅, and (EKER)₅. The stability of the secondary structure was examined at three pH values in the presence of urea and NaCl. The results presented here underscore the combined prominent effects of the charge sequence pattern and the type of positively charged monomers on secondary structure formation. Additionally, (ERRE)₅ readily aggregated across a wide range of pH. In contrast, sequences with the same charge pattern, (EKKE)₅, as well as the sequences with the equivalent amino acid content, (ERER)₅, exhibited no aggregate formation under equivalent pH and concentration conditions.